The present invention relates to a static electricity removing structure for a portable electronic device which incorporates a printed circuit board with an electronic component and a wiring pattern formed thereon.
Downsizing and lightweight designs for the present portable electronic devices have been improved in accordance with related progresses in semiconductor techniques and mounting techniques. However, downsizing and lightweight designs of electronic devices possibly encounter electrostatic problems.
Static electricity enters from the outside of a casing into a portable electronic device. Some of electronic components, such as transistors, are weak in durability against the static electricity. Thus, there is a possibility that static electricity may break the sensitive electronic components. Furthermore, the static electricity causes noises. If such noises enter into a signal line, for example, via a switch, various control circuits will malfunction.
FIGS. 3 and 4 show some of conventional static electricity removing structures applied to portable electronic devices.
In FIG. 3, a portable electronic device comprises a printed circuit board 1. An electronic component 2 and a wiring pattern 3 are formed on the printed circuit board 1. The printed circuit board 1 is securely fixed in a casing 4. Static electricity tends to enter into the casing 4 via a clearance or hole 5. An insulating sheet 6 is provided in the vicinity of the electronic component 2 and the wiring pattern 3 as measures for preventing the static electricity.
FIG. 4 shows a silicone resin 7 molding the electronic component 2 and the wiring pattern 3 as other measures for preventing the static electricity.
However, providing the insulating sheet 6 in the vicinity of the electronic component 2 and the wiring pattern 3 or molding them by the silicone resin 7 is not preferable in that the number of parts will increase and the working steps in a manufacturing process will increase correspondingly. This possibly raises the product costs and worsens the productivity in the manufacturing process.